A mobile WiMAX (Worldwide interoperability for Microwave Access) system realized by applying to mobile communication a WiMAX technique, which is becoming a focus of attention in recent years, includes an MS, which is a mobile station that receives a service by subscribing to the system, a BS, which is a base station configured to be connectable to the MS and an ASN-GW (Access Service Network Gateway), which is a connection device for connecting the MS to a network via the BS.
FIG. 1 is a diagram illustrating one configuration example of a general WiMAX system.
The WiMAX system shown in FIG. 1 is provided with DHCP server 1003, ASN-GW 1004, BS 1005 and MS 1006.
DHCP server 1003 is a server which is located on CSN (Connectivity Service Network) 1001 and has a DHCP (Dynamic Host Configuration Protocol) function which is a protocol for automatically setting an IP (Internet Protocol) address in MS 1006.
ASN-GW 1004 is a connection device for connecting CSN 1001 to ASN (Access Service Network) 1002. Furthermore, ASN-GW 1004 is connected to DHCP server 1003 and BS 1005.
BS 1005 is a base station located on ASN 1002 and configured to be connectable to MS 1006.
MS 1006 is a mobile station which is movable and communicates with CSN 1001 via BS 1005 and ASN-GW 1004.
Furthermore, for not only such a WiMAX system but also a communication system that communicates packet data, JP2005-124077A discloses a technique of performing communication by compressing a packet header of the packet data for reducing on the communication bandwidth. An example of such a technique is a PHS (Payload Header Suppression) rule.
The PHS rule is a mechanism of payload header compression capable of efficiently operating a communication channel by reducing information of a redundant packet header and thereby reducing bands used.
FIG. 2 is a diagram illustrating an example of compression of a packet header to which a predetermined PHS rule is applied.
As shown in FIG. 2, part of the packet header section to which the predetermined PHS rule is applied, of the packet data made up of MAC (Media Access Control) header, IP header and UDP (User Datagram Protocol)/TCP (Transmission Control Protocol) header and data, and CRC (Cyclic Redundancy Check) field is compressed. Here, the IP header section of the packet header is compressed.
FIG. 3 is a diagram illustrating the PHS rule.
In FIG. 3, a packet header made up of A, B, C, D and E is transmitted from the transmitting side which is a transmission apparatus to the receiving side which is a receiving apparatus via a radio zone. Here, A, B, C, D and E are data in byte units. Applying the PHS rule to this packet header causes the packet header to be compressed.
Here, desired data can be compressed using “PHSM (PHS-Mask)” which is information indicating the position to be compressed and “PHSF (PHS-Field)” which is the content (information) of data to be compressed. For example, by setting “1” in “PHSM” of A, C and E respectively at the transmission apparatus, A, C and E are compressed and transmitted. That is, as shown in FIG. 3, the packet header in the radio zone is made up of B and D. Furthermore, by setting respective values in “PHSF” of compressed A, C and E, “PHSF” in which the value is set is transmitted from the transmitting side to the receiving side, and compressed A, C and E are reconstructed on the receiving side respectively.
Hereinafter, a case will be described where the aforementioned PHS rule is applied to the WiMAX system shown in FIG. 1.
FIG. 4 is a diagram illustrating an example of an internal configuration of ASN-GW 1004 shown in FIG. 1.
As shown in FIG. 4, ASN-GW 1004 shown in FIG. 1 is provided with BS interface section 1041, service flow generation section 1042, CSN data transfer section 1043 and PHS rule storage section 1044.
BS interface section 1041 has an interface function for BS 1005.
Service flow generation section 1042 reads the PHS rule stored in PHS rule storage section 1044 and transmits the read PHS rule to BS 1005 via BS interface section 1041.
CSN data transfer section 1043 has an interface function for CSN 1001.
PHS rule storage section 1044 stores the PHS rule manually created beforehand.
Hereinafter, a method for MS 1006 to subscribe to the WiMAX system shown in FIG. 1 (Network Entry) will be described.
FIG. 5 is a sequence diagram illustrating a method for MS 1006 to subscribe to the WiMAX system shown in FIG. 1.
First, in step 81, an RNG-REQ (Ranging-Request) message which is a ranging request signal is transmitted from MS 1006 to BS 1005. In step 82, an RNG-RSP (Ranging-Response) message which is a response signal to the RNG-REQ message is transmitted from BS 1005 to MS 1006.
Next, in order to perform negotiation on information on various types of capability (capacity), in step 83, an SBC-REQ (Station Basic Capability-Request) message is transmitted from MS 1006 to BS 1005. In step 84, an SBC-RSP (Station Basic Capability-Response) Message which is a response signal to the SBC-REQ message is transmitted from BS 1005 to MS 1006.
Next, in step 85, a REG-REQ (Registration-Request) message which is a registration request signal is transmitted from MS 1006 to BS 1005. In step 86, a REG-RSP (Registration-Response) message which is a response signal to the REG-REQ message is transmitted from BS 1005 to MS 1006.
A DSA-REQ (Dynamic Service Addition-Request)/RSP/ACK (Acknowledge) message for establishing a new service flow is transmitted/received between BS 1005 and MS 1006 one time for an uplink and a downlink in steps 87 to 92. In this case, the DSA-REQ message transmitted from BS 1005 to MS 1006 includes the PHS rule.
After that, in steps 93 to 96, MS 1006 requests an IP address to DHCP server 1003 via BS 1005 and ASN-GW 1004, and DHCP server 1003 assigns an IP address to MS 1006.
However, generation of the aforementioned PHS rule involves the following problems.
A first problem is that since the PHS rule is manually created, unless the content of a packet is known beforehand, it is possible neither to specify the compression location nor to generate the PHS rule.
A second problem is that since the PHS rule cannot be generated unless the content of a packet is known beforehand, it is only fixed IP addresses that can be handled. That is, when an IP address is assigned using DHCP, the IP address part cannot be compressed.